1. Field of the Invention
The present invention relates to an alternating current generator, and in particular, to a power source for the alternating current generator.
2. Description of the Related Art
A number of alternating current generators that combine single-phases of 100 V and 200 V for use in construction sites, various event sites, and the like are needed. In order to respond to such a requirement, a conventional example of an electric generation apparatus, for example, as shown in FIGS. 10 to 12 is disclosed in Japanese Patent Laid-Open Publication No. Sho 63-87157.
That is, in FIG. 10 the conventional example bisects, for example, an armature winding W into W1 and W2 out of a three-phase stator that consists of armature windings U, V, and W connected to a neutral point O at a phase difference of 120 degrees (electric angle), respectively, then connects the armature windings W1 and W2 in series, and in addition, is equipped with a configuration having a connection change device (not shown) for connecting the armature winding W1 to the neutral point O while making only the winding W1 a reverse phase (shown in broken lines). When the armature windings W1 and W2 are connected in series, the conventional example can be used as a three-phase power source by change operation of the connection change device, and, as shown in voltage vectors of FIG. 11, a three-phase alternating current of 200 V each is output from terminals L1, L2, and L3.
On the other hand, when only the armature winding W1 is connected to the neutral point O while being made the reverse phase by the change operation of the connection change device (not shown), the conventional example can be used as a single-phase three-wire power source as shown in electric vectors of FIG. 12. A single-phase alternating current of 100 V is output from between terminals L1 and N, and between terminals L2 and N; a single-phase alternating current of 200 V is output from between terminals L1 and L2. In the meantime, although as shown in FIG. 10, grounding wires Le and Le′, and a neutral wire having the neutral terminal N are respectively connected to the neutral point O, and the grounding wires Le and Le′ are connected to the ground, the grounding wire Le is separated at the same time as a change is performed to the single-phase three-wire power source, and the grounding wire Le′ is connected to the neutral terminal N, thereby the neutral terminal N is grounded to the ground through the grounding wire Le′.
However, there are problems in the conventional example as follows:
(1) The conventional connection change device needs a changeover switch having a contact capacity that can tolerate an output electric power amount. As a result, costs become high, and the electric wiring becomes complex.
(2) When the single-phase three-wire power source is configured in accordance with the conventional example, a voltage of an armature winding that is made the reverse phase appears in the neutral wire terminal N of the single-phase three-wire power source, a neutral terminal. As a result, the neutral terminal loses its property of being a neutral point such that an electric potential thereof is the same as that of the ground. Consequently, although a connection of the grounding wire Le is changed from the neutral point O to the terminal N, this accelerates the problem of item (1).
(3) In the conventional example, alternating current electric powers of the three-phase power source and the single-phase three-wire power source cannot be simultaneously output, and a utilization factor of the alternating current generator also becomes low.
(4) Because the conventional example provides a configuration of separating an armature winding of the three-phase power source into two, thereby performing a change operation, and thus the single-phase three-wire power source is made, a winding number of the armature winding of the single-phase three-wire power source depends on that of the three-phase power source. As a result, an output voltage from the three-phase power source to the single-phase three-wire power source cannot be freely set, and in particular, this makes it difficult to handle overseas situations where voltage specifications are various.
Consequently, it is desirable to provide an alternating current generator that does not need the changeover switch, can simultaneously output the alternating current electric powers of the three-phase power source and the single-phase three-wire power source, and is high in the utilization factor thereof; wherein furthermore, the winding number of the armature winding of the single-phase three-wire power source does not depend on that of the three-phase power source; wherein as a result, the output voltage from the three-phase power source to the single-phase three-wire power source can be freely set; and wherein in particular, this makes it possible to handle the overseas situations where the voltage specifications are various.